Orion unmanned plane, with its 132-foot wingspan, is intended to stay aloft for up to five days. (Aurora Flight Sciences)

Long-endurance flight has long been the holy grail of U.S. unmanned airborne intelligence, surveillance and reconnaissance, but the quest so far has been worthy of a Monty Python film. The composite-winged Global Observer crashed. The hydrogen-powered Phantom Eye lost a wheel. The helium-filled High Altitude Long Endurance airship ditched in a Pennsylvania forest. The Blue Devil 2 airship was canceled; so was the Long Endurance Multi-intelligence Vehicle.

Among those trying to end the flying circus is a team of engineers at the Air Force’s secretive Big Safari aircraft engineering group, based at Wright-Patterson Air Force Base, Ohio.

Big Safari has been working with Aurora Flight Sciences of Manassas, Va., to assemble a twin-engine drone called Orion. With a 132-foot wingspan and off-the-shelf engines, Orion is supposed to fly for 120 hours, five times longer than today’s Predator and Reaper drones. Aurora describes Orion as an airborne “ISR truck.”

So far, it hasn’t made its first flight, and the question is whether Orion will be a lame duck even if it finally gets off the ground. The Air Force has no money in its long-range budget to buy a fleet of Orions or any other drone, an Air Force official said. Advocates are hoping a series of successful Orion flights might swing the budget dynamics back in their favor, although it looks like a long shot.

Cue the Reapers

Money that could have gone toward work on a new plane has been set aside to improve the range of today’s Reaper drones. The Air Force has agreed to an extended-range version of the hunter-killer from General Atomics Aeronautical Systems. Company officials said they have briefed the new variant to the Pentagon’s top intelligence official, Michael Vickers, who has visited the company’s facility in California.

The company and the Air Force are negotiating a contract to give some Reapers new wings so they can carry fuel pods. The range extension would be modest — from today’s 20 hours out to 28 hours with a typical mix of missiles and sensors — but it would be done as a “quick-reaction capability.”

The Reaper contract is emblematic of a shift in the Pentagon’s ambition toward ISR innovations.

The General Atomics Reaper proposal landed on fertile ground at the Pentagon.

“I’ve got a vendor who says, ‘Fairly cheaply, I can extend the range a lot,’” an Air Force official said.

“A lot” is a relative term. General Atomics calculates it can increase endurance from 30 to 38 hours for a Reaper carrying a light load, and 20 to 28 hours with a more typical load. The wing work would be done in the field, probably by General Atomics, on an undisclosed number of Reapers. Workers would replace the Reaper’s 66-foot wingspan with wings of the same length but strong enough to carry two fuel tanks and four Hellfire missiles. A fuel tank would ride on each wing’s inner hard point, and two Hellfires would be carried on each wing’s outer station.

Even General Atomics acknowledges that a longer-legged Reaper would have nothing like Orion’s 120 hours.

“I wouldn’t say they’re in the same space,” said Chris Pehrson, the company’s director of strategic development.

But there are other advantages.

“If you had a different platform, like an aerostat or an Orion or something like that, you need a whole different set of infrastructure to support it,” Pehrson said.

The Air Force wants to make as few changes in the field as possible. In fact, the service rejected a proposal to install new 80-foot or even 88-foot wings on the Reapers. That could have bumped endurance out to 42 hours, depending on the load, but wouldn’t have fit in existing shelters at bases in Afghanistan and elsewhere, an Air Force official said.

Not dead yet

Budget pressures and the plan to pull most troops out of Afghanistan are pushing the services to rely on aircraft they already have, said retired Lt. Gen. David Deptula, the Air Force deputy chief of staff for intelligence from 2006 to 2010. But Deptula said that’s shortsighted. Down the road, he said, planners will discover that with today’s aircraft and sensors, they can’t collect all the intelligence they need without busting budgets.

Deptula’s former company, MAV6, was driven from 75 employees down to a handful by the Air Force’s decision to cancel development of an airship called the M1400, but better known as Blue Devil 2, after the sensor package it would have carried.

Still, Air Force unmanned aerial vehicle planners have not shut the door completely on a new aircraft, and they’re watching developments in two experimental systems closely. One is Boeing’s self-funded Phantom Eye, which flew for 66 minutes in February. Powered by small-truck engines that use hydrogen as fuel, Phantom Eye was designed to carry only 450 pounds of equipment. If the flights go as planned, Boeing wants to build an operational version that should be able to carry 2,000 pounds.

Unlike Phantom Eye, Orion was designed specifically with the Air Force’s long-endurance needs in mind. It’s supposed to carry 1,000 pounds of surveillance and communications equipment at an altitude of 20,000 feet for five days, according to Aurora’s website.

The Air Force’s ISR planners have had to be patient, though. Orion’s development has unfolded more slowly than originally envisioned for reasons that are not entirely clear.

The program started about four years ago, when the Air Force persuaded the Pentagon’s Rapid Fielding office to conduct a competition for a Medium Altitude Global ISR Communication demonstrator. One idea is to use Orion as the equivalent of a communications satellite or cellphone tower in the battle zone or at home after a natural disaster.

How long is enough?

The service’s ISR planners are looking at the claims for all these aircraft with the eyes of a Missourian: Show me, they say. On Orion, no money has been committed beyond the inaugural flight.

“If they can achieve first flight, then maybe we would be interested in contributing to a long-endurance flight,” said an Air Force official.

The obvious advantage of long endurance is that it would provide more time over surveillance targets.

“We spend anywhere from 20 to maybe even as high as 40 percent of our time transiting our RPAs [remotely piloted aircraft] from base to the operational area where they’re at,” said recently retired Air Force Maj. Gen. James O. Poss, who was deputy chief of staff for intelligence until February.

Flying longer is good, but it’s less obvious just how much endurance is the right amount. The Air Force’s A9 Studies and Analysis Directorate tried to get at that question last year with a detailed study that has not been publicly released.

“It showed that there were two sweet spots when it comes to endurance,” Poss said. “One for something that flies for about a day, 24 hours, and then something that flies about a week.”

The finding was an eye-opener for those who assumed flying longer was always better.

“We were looking at a whole bunch of exotic concepts to fly for a month, or whatever, and what we kind of proved was that flying over a week was kind of overkill,” Poss said. “If you think about it practically, if you’ve got a no-fail military mission, you’re probably never going to rely on a single air vehicle to do that. It’s just too much risk.”